The present invention relates to a developing device and an image forming apparatus.
In a conventional image forming apparatus, a developing device is provided with a developer supporting member. The developer supporting member may have a crown shape having a difference in outer diameters between a center portion thereof and a end portion thereof in an axial direction thereof. Accordingly, it is possible to maintain a constant nip amount with respect to an image supporting member (refer to Patent Reference).    Patent Reference: Japan Patent Publication No. 2001-350351
In the conventional developing device described above, even though the developer supporting member has a crown shape, when the developer supporting member has an elastic layer having a high hardness, and an end portion thereof tends to wobble to a large extent, the nip amount tends to decrease at the end portion. Accordingly, it is difficult to develop a static latent image on the image supporting member, thereby causing a blank portion in an image.
In view of the problem described above, an object of the invention is to provide a developing device and an image forming device, in which it is possible to solve the problems of the conventional developing device. In the developing device, in a state that a film member is disposed between an image supporting member and a developer supporting member, it is arranged such that the film member is extended with a force within a specific range when the image supporting member and the developer supporting member rotate. Accordingly, it is possible to obtain a sufficient nip amount between the image supporting member and the developer supporting member, thereby preventing a blank portion in an image due to an insufficient nip amount.
Further objects of the invention will be apparent from the following description of the invention.